With the increased significance of recapturing scrap materials, particularly scrap metal, for recycling and reuse that has resulted from both environmental considerations and shortages in raw materials, the shredding and separating of large items of metal, for example, automobiles, trucks and white goods such as appliances, has developed into a significant industry. The equipment required to perform this task is large and complicated. The equipment normally icludes a hammer mill for breaking large items of metal and the like into smaller and denser "shredded" pieces of metal and various separation means for separating the metals both as to size and type of metal from the non-metallic materials. Shredded or shredding as used in this discussion refers to the breaking down of large, bulky items, such as automobile bodies, into smaller more easily handled pieces of metal and non-metallic materials. Since a large amount of dust and particulate matter is produced by this process, the equipment required also includes extensive dust collection devices. The typical dust collection device utilized comprises a cyclone separator device for separating the larger particles of dust and particulate material from the smaller; and a wet scrubber for the removal of the smaller particles and gaseous materials prior to the release of any exhaust into the atmosphere. The above mentioned cyclones and scrubber devices are well known and typical in the environmental field. The cyclone separator devices and scrubber are connected to the hammer mill by duct work through which dust and particulate material is drawn from the hammer mill to the dust collection equipment by means of a draw fan which creates a negative pressure between the fan and hammer mill within the duct work so that dust and particulate matter is drawn from the hammer mill to the dust collection equipment. A positive pressure is maintained between the fan and the scrubber. A typical example of the type of equipment utilized in this industry is the Newell Shredding System which is manufactured by the Newell Manufacturing Company, San Antonio, Texas.
Frequently, the source for scrap metal to be shredded in the above described system are old car bodies and appliances. The car body or appliance is fed intact into the hammer mill where it is shredded as discussed above. Periodically, despite severe prevention methods and continuous inspections, a car body is introduced into the system complete with its gasoline tank intact containing in general hydrocarbons and particularly gasoline. When this gasoline tank is introduced into the hammer mill, it is ruptured and any hydrocarbons or gasoline present are vaporized to fumes which are drawn into the duct work system, dust collector, fan and scrubber. The hammer mill at this time also creates sparks as a result of contact between the metal being shredded and the metallic elements of the hammer mill. These sparks combined with the disbursed hydrocarbon vapors, the particulate nature of dust and the other particulate matters present in the system frequently form the basis for violent explosions, which have the capability of causing great destruction and human injuries.